Here is the complete "VIOLENT CRIMINAL HISTORY" for GZ.
He pushed a guy in a bar! (Allegedly)
In 2005, George Zimmerman — 21 at the time — was at a bar near the University of Central Florida when a friend was arrested by state alcohol agents on suspicion of serving underage drinkers, according to an arrest report.

Zimmerman was talking with his friend, became profane and pushed an agent who tried to escort him away, the report said. Authorities said he was arrested after a short struggle.
Charged with resisting arrest without violence, he avoided conviction by entering a pretrial-diversion program, something common for first-time offenders.
A month later, court records show, a woman filed a petition for an injunction against Zimmerman, citing domestic violence. It's unclear what led to the petition, but Zimmerman responded by filing a petition of his own the following day.
Records show injunctions were later issued in both cases. Reached by email, the woman would not comment on her past with Zimmerman or his current situation.
...so his friend was getting harassed/roughed up by a couple of guys who were not uniformed cops. GZ defends his friend, just like any bro in a bar is going to do. When it became clear they were law enforcement, he stopped. IF he ever shoved the agent in the first place. I've read the report was 'enhanced' like cops often do.
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http://www.thecrimson.com/article/2012/4/2/Troia-Zimmerman-justice/
Did Zimmerman racially profile Martin in judging him “suspicious”? Here the distinction between racial profiling and holistic profiling is relevant. Zimmerman’s friend Frank Taaffe said young black males had committed a string of recent robberies in the diverse neighborhood. If Martin fit the profile of these specific suspects, was unfamiliar in the neighborhood, and was acting strangely in Zimmerman’s mind by walking behind houses, Zimmerman’s judgment was appropriate.
There are three eyewitnesses in the case; two corroborate Zimmerman’s account. One says he saw Zimmerman, below Martin, crying for help while Martin beat him. Austin Brown, a black teenager, says he saw Zimmerman on the ground “moaning and crying for help.” Brown’s mother has since said police pressured him into giving more information than he remembered, but he repeated the claim afterwards. She may simply be concerned that her son will suffer backlash like Joe Oliver, a black supporter of Zimmerman, who says he has a “target on my back.” A third eyewitness says it was too dark to tell who was who.
Only non-eyewitnesses to the scuffle have corroborated Martin’s family’s account.
Martin was repeatedly suspended from school, including for graffiti; was found with 12 pieces of women’s jewelry and a screwdriver in his backpack, a possible burglary tool; or that he might have punched a bus driver. The Martin family’s attorney said Trayvon’s past was “irrelevant,” yet has highlighted Zimmerman’s criminal history.